The UDP or TCP port number used as a source
port for this sender in this session. If the
IP protocol in use, specified by wfRsvpResvProto-
col is 50 (ESP) or 51 (AH), this represents a
generalized port identifier (GPI). A value of
zero indicates that the IP protocol in use does
not have ports. This object may not be changed
when the value of the RowStatus object is
'valid'.